A typical cushion uses elastic foam material for suitably distributing pressure from the body over a relatively large surface area of the body being supported by the cushion, such as a person lying on a mattress, a person seated in a couch, or an animal resting on a veterinary surgeon's table.
When used in combination with some type of less elastic overlying layer, the elastic foam underlying layer in the cushion counteracts the deepest depressed parts in the overlying layer in order to provide an increased counter-pressure against the body. To achieve a reasonably limited cushion thickness, the underlying layer is typically arranged in the form of a highly-elastic foam layer or a spring base with mechanical springs to provide suitable support to the user.